<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>实验2_2</title>
		<style>
			div {
				color: skyblue;
			}

			.d1 {
				font-size: 30px;
			}

			.d1.d2 {
				background-color: pink;
			}

			#d3 {
				background-color: yellowgreen;
			}

			div[ab="d4"] {
				background-color: red;
			}
		</style>
	</head>
	<body>
		<div>1</div>
		<div class="d1">1</div>
		<div class="d1 d2">2</div>
		<div id="d3">3</div>
		<div ab="d4">4</div>
	</body>
</html>